Super-insulating,ultralight and high-strength mullite-based nanofiber composite aerogels

Ceramic nanofiber aerogel is one of the most attractive insulation materials in recent years. However, its practical application ability is limited at high temperature due to high radiation heat transfer. Herein, we constructed a novel closed-cell/nanowire structured mullite-based nanofiber composite aerogel via electrospinning technology and solvothermal synthesis method. Hollow TiO₂ spheres were used as pore-making material and infrared opacifier to reduce fiber solid heat conduction and high temperature radiation heat transfer simultaneously. In addition, TiO₂ nanowires grown in-situ on the fiber surface further decrease the radiation heat transfer of aerogel and improve the mechanical properties. The unique structure endows the aerogel with high mechanical robustness (0.32–0.35 MPa, 10% strain), low density (39.2–47.5 mg/cm³) and ultralow thermal conductivity (~0.017 W m^?1 K^?1 at 25 ℃ and ~0.056 W m^?1 K^?1 at 1000 ℃). This work offers a novel strategy for the development of ceramic nanofiber aerogel at high temperature.